Graphics Command  Generation Device and Graphics Command Generation Method

ABSTRACT

An intermediate command generation unit generates intermediate commands, which are intermediate rendering commands having model data for rendering an object. 
     A graphics command conversion unit converts the generated intermediate commands into a graphic command sequence for execution by a graphics processor. An identity determination unit determines whether a state of a graphics command to be generated from an intermediate command is the same as a state of the graphics command generated previously. A graphics command generation unit generates a graphics command determined by the identity determination unit as not having the same state, and does not generate a graphics command determined as having the same state, defining the command as a redundant command.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technology of generating a graphicscommand and, more particularly, to a technology of generating a graphicscommand from an intermediate command.

2. Description of the Related Art

High-quality graphics are extensively used now as personal computers andgaming devices are used to run applications like games and simulationsthat use high-quality three-dimensional graphics and to play back imagecontent in which actual footage and computer graphics are blended.

Generally, graphics processing is performed by using a CPU and agraphics processing unit coordinated with each other. A CPU is ageneral-purpose processor capable of general purpose computation, whilea GPU is a special-purpose processor for advanced graphics computation.A CPU performs geometric computation such as projection transformationbased on a three-dimensional model of an object. A GPU receives vertexdata etc., from a CPU and performs rendering accordingly. A GPUcomprises special-purpose hardware such as a rasterizer and a pixelshader and performs graphics processing using a pipeline process. Insome recent GPUs, the shader capability is programmable as exemplifiedby a program shader. In general, a graphics library is provided tosupport shader programming.

To render an object, the CPU needs to generate a graphics commandexecuted by the hardware of the GPU and deliver the generated command tothe GPU. Generation of a graphics command requires much CPU time. Thisis sometimes addressed by introducing an intermediate command anddividing the process of generating a graphics command into two stagesincluding generation of a intermediate command and conversion from theintermediate command to the graphics command. By executing generation ofan intermediate command and conversion from the intermediate command toa graphics command in separate threads, it is possible to execute inparallel the process of generating an intermediate command and thenconverting the intermediate command into a graphics command, andprocesses other than graphics processing such as physical modelcomputation for rendering subsequent frames. As a result of that, theCPU utilization can be improved.

-   [patent document 1] JP2008-123520

However, conversion from a plurality of intermediate commands intographics commands may result in the same graphics command beingrepeatedly executed in spite of the fact that the state remainsunchanged in a sequence of generated graphics commands. Due to thisredundancy, the efficiency of execution is lowered.

SUMMARY OF THE INVENTION

The present invention addresses the problem and a purpose thereof is toprovide a technology capable of improving the efficiency of executinggraphics commands generated from intermediate commands.

The graphics command generating device according to at least oneembodiment comprises: an intermediate command generation unit configuredto generate intermediate commands, which are intermediate renderingcommands having model data for rendering an object; and a graphicscommand conversion unit configured to convert the generated intermediatecommands into a graphic command sequence for execution by a graphicsprocessor. The graphics command conversion unit comprises: an identitydetermination unit configured to determine whether a state of a graphicscommand to be generated from an intermediate command is the same as astate of a graphics command generated previously; and a graphics commandgeneration unit configured to generate a graphics command determined bythe identity determination unit as not having a state that is the same,and to not generate a graphics command determined as having the samestate, defining said command as a redundant command.

Another embodiment of the present invention relates to a graphicscommand generation method. The graphics command generation methodcomprises: generating intermediate commands, which are intermediaterendering commands having model data for rendering an object; andconverting the generated intermediate commands into a graphic commandsequence for execution by a graphics processor. The convertingcomprises: determining whether a state of a graphics command to begenerated from an intermediate command is the same as a state of agraphics command generated previously; and generating a graphics commanddetermined as not having a state that is the same, and not generating agraphics command determined as having the same state, defining saidcommand as a redundant command.

Optional combinations of the aforementioned constituting elements, andimplementations of the invention in the form of methods, apparatuses,systems, computer programs, data structures, and recording mediums mayalso be practiced as additional modes of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures, in which:

FIG. 1 shows the configuration of the graphics processing systemaccording to the embodiment;

FIG. 2 shows the configuration of the graphics command generationdevice;

FIGS. 3A-3D show how graphics commands are generated from intermediatecommands;

FIG. 4A illustrates the method of computing a transition cost of modeldata by using the transition cost computation unit of FIG. 2, and FIG.4B illustrates the method of assigning a sort key to the model data byusing the sort key assigning unit 20;

FIG. 5 is a flowchart showing the steps of generating graphics commandsby the graphics command generation device according to the embodiment;

FIG. 6 is a flowchart showing the details of conversion into graphicscommands in step S60 executed by the graphics command conversion unit;

FIG. 7 shows a system where an intermediate command sequence isgenerated in a plurality of processes, and sorting and redundancyelimination are performed in a single rendering process;

FIG. 8 shows a system where an intermediate command sequence forrendering is generated by a plurality of servers, and sorting andredundancy elimination are performed in a client which communicates withthe server; and

FIG. 9 shows a system where an intermediate command sequence isgenerated by a plurality of clients and sorting, and sorting andredundancy elimination are performed in a server which communicates withthe plurality of clients.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by reference to the preferredembodiments. This does not intend to limit the scope of the presentinvention, but to exemplify the invention.

FIG. 1 shows the configuration of the graphics processing systemaccording to the embodiment. The graphics processing system comprises amain processing unit 100, a graphics processing unit 140, a systemmemory 180, and a local memory 160.

The main processing unit 100 may be a single main processor, or amultiprocessor including a plurality of processors, or a multicoreprocessor including a plurality of processor cores integrated in asingle package. In this case, the main processing unit 100 isexemplified by a heterogeneous multicore processor including a mainprocessor 101 and a plurality of subprocessors 110. The main processor101 and the plurality of subprocessors 110 are connected to a bust 120.A system memory 180 is connected to the bus 120 via a memory interface170. The main processor 101 and the plurality of subprocessors 110 arecapable of writing and reading data in the system memory 180 via the bus120.

An external device 190 is connected to the bus 120 via an input andoutput interface (hereinafter, “IOIF”) 130. The external device 190includes the graphics processing unit 140 and the local memory 160.However, the illustrated system is by way of example only.

The graphics processing unit (hereinafter, simply referred to as “GPU”)140 is a graphic chip provided with a graphic processor core and iscapable of reading and writing data in the memory 160 via a local bus150.

The main processing unit 100 and the GPU 140 are connected via the IOIF130. The main processing unit 100 and the GPU 140 can exchange data viathe IOIF 130.

The main processing unit 100 generates a rendering command for renderingan object and queues the commands in a command buffer provided in thesystem memory 180. The GPU 140 sequentially reads the rendering commandsstored in the command buffer and processes the read commands.

The main processing unit 100 generates geometry data such as vertexcoordinate values, vertex color, normal vector, and UV values, based onthe three-dimensional model of an object, and stores the geometry datain the system memory 180. Further, the main processing unit 100 stores atexture to be mapped to the surface of a polygon in the system memory180. Still further, the main processing unit 100 reads a shader programfrom a recording medium such as a hard disk and stores the program inthe system memory 180.

The memory area of the system memory 180 is memory-mapped to the I/Oaddress space. The GPU 140 is capable of reading the memory area of thesystem memory 180 memory-mapped to the I/O address space via the IOIF130.

The memory area of the system memory 180 storing the geometry data, thetexture, and the shader program is memory-mapped to the I/O addressspace in a memory provided in the controller of the IOIF 130. The GPU140 reads the geometry data, the texture, and the shader programmemory-mapped to the I/O address space via the IOIF 130. The GPU 140stores in the local memory 160 data necessary for graphics computationsuch as the geometry data, the texture, etc., read from the systemmemory 180.

The GPU 140 generates rasterized data of a polygon according to theshader program, using the geometry data, and writes pixel data in theframe buffer in the local memory 160. Further, the GPU 140 maps thetexture on the surface of the polygon and writes the pixel dataoccurring after texture mapping in the frame buffer.

FIG. 2 shows the configuration of the graphics command generation device200. The graphics command generation device 200 is implemented in themain processing unit 100. If the main processing unit 100 is a multicoreprocessor, a thread on the main processor 101 or on at least one of thesubprocessors 110 implements the functions of the graphics commandgeneration device 200.

The graphics command generation device 200 includes a transition costcomputation unit 10, a sort key assigning unit 20, an intermediatecommand generation unit 30, a model data storage unit 32, a work datastorage unit 34, a sorting unit 40, and a graphics command conversionunit 50. The graphics command conversion unit 50 includes an identitydetermination unit 60, a graphics command generation unit 70, and astate cache 80.

An intermediate command includes model data and work data for renderingof an object. Model data represents information not updated betweenframes, such as geometry data, a texture, and a shader program, and isstored in the model data storage unit 32. Work data representsinformation updated for each frame, such as the position and orientationof an object, and is stored in the work data storage unit 34.

The transition cost computation unit 10 reads model data from the modeldata storage unit 32, computes a transition cost incurred when the modeldata makes a transition between two intermediate commands. Thetransition cost computation unit 10 stores the transition cost in themodel data storage unit 32.

The sort key assigning unit 20 determines the sequence in which themodel should make a transition in accordance with the transition cost.The sort key assigning unit 20 assigns a sort key to the model data inaccordance with the determined sequence and stores the resultant modeldata in the model data storage unit 32. The sort key assigning unit 20starts with a given item of model data, e.g., with the model data thatmost occupies the displayed screen area. The sort key assigning unit 20determines the sequence in which the model data should make a transitionby scanning the model data in the ascending order of the transitioncost, and assigns sort keys to the model data according to thedetermined sequence of transition.

The intermediate command generation unit 30 reads the model data foreach frame from the model data storage unit 32, reads the work data fromthe work data storage unit 34, and generates an intermediate commandhaving the model data and the work data from a scene graph includinginformation on an object to be rendered.

The sorting unit 40 changes the order of execution of a plurality ofintermediate commands generated by the intermediate command generationunit 30, in accordance with the sort keys assigned to the model data ofthe respective intermediate commands.

The graphics command conversion unit 50 converts the plurality ofintermediate commands, the order of execution of which is changed by thesorting unit 40, into a graphics command sequence for execution by thegraphics processor.

The identification unit 60 in the graphics command converter 50determines whether the state of a graphics command generated from anintermediate command is identical to the state of a graphics commandgenerated previously. The graphics command generation unit 70 generatesa graphics command determined by the identification determination unit60 as not being identical in state to the previously generated graphicscommand. The graphics command generation unit 70 does not generate agraphics command determined as being identical in state to thepreviously generated graphics command, defining such a command as aredundant command.

More specifically, the state of the graphics command generated by thegraphics command generation unit 70 is cached in the state cache 80. Theidentity determination unit 60 refers to the state cache 80, using thestate of the graphics command that should be generated from theintermediate command as a key. If a cache hit occurs, the identitydetermination unit 60 determines that the state of the graphics commandthat should be generated from the intermediate command is identical tothe state of the previously generated graphics command. In the absenceof a cache hit, the identity determination unit 60 updates the statevalue cached in the state cache 80 with the state value of the graphicscommand that should be generated from the intermediate command. In theevent of a cache hit, the graphics command generation unit 70 definesthe graphics command as a redundant command and does not generate thegraphics command. In the absence of a cache hit, the graphics commandgeneration unit 70 generates the graphics command.

The graphics command generated by the graphical command generation unit70 is delivered to the GPU 140 and executed by the hardware of the GPU140 so as to render the object.

FIGS. 3A-3D show how graphics commands are generated from intermediatecommands.

FIG. 3A shows an intermediate a sequence of intermediate commandsgenerated by the intermediate command generation unit 30. In thisexample, DrawPacket1, DrawPacket2, and DrawPacket3 are generated asintermediated commands in the stated order. FIG. 3 shows a sequence ofintermediate commands sorted by the sorting unit 40. The order ofexecution of the two intermediate commands DrawPacket1 and DrawPacket2is changed as a result of sorting with the result that the intermediatecommands are executed in the order DrawPacket2, DrawPacket1, andDrawPacket3. By executing the intermediate commands in the order ofexecution of the intermediate commands generated by the sorting unit 40,the transition cost of the model data will be lowered than when theintermediate commands are executed in the order of execution generatedby the intermediate command generation unit 30.

FIGS. 3C and 3D show how the graphics command converter 50 convertsintermediate commands into graphics commands.

For the purpose of comparison, a description will first be given, withreference to FIG. 3C, of a graphics command sequence generated byconversion from intermediate commands without using the identitydetermination unit 60.

The graphics command generation unit 70 converts the first intermediatecommand DrawPacket2 in the intermediate command sequence sorted by thesorting unit 40 into a graphics command sequence as indicated below.

SetTexture(A);

SetVertexShader(P);

SetFragmentShader(X);

DrawIndexArray(J);

This will be referred to as the first graphics command sequence.SetTexture is a graphics command for defining a texture, SetVertexShaderis a graphics command for defining a vertex shader program,SetFragmentShader is a graphics command for defining a fragment shader,DrawIndexArray is a graphics command for performing rendering inaccordance with a parameter and a program defined. A, P, X, and J in theparentheses denote states. For example, the argument A of the functionSetTexture( ) denotes a texture ID, the argument P of SetVertexShader( )denotes the shader ID or the address of the program on the memory.

Subsequently, the graphics command generation unit 70 converts thesecond intermediate command DrawPacket1 in the intermediate commandsequence sorted by the sorting unit 40 into a graphics command sequenceas indicated below.

SetTexture(B);

SetVertexShader(P);

SetFragmentShader(Y);

DrawIndexArray(K);

This will be referred to as the second graphics command sequence.

Further, the graphics command generation unit 70 converts the thirdintermediate command DrawPacket3 in the intermediate command sequencesorted by the sorting unit 40 into a graphics command sequence asindicated below.

SetTexture(B);

SetVertexShader(P);

SetFragmentShader(Y);

DrawIndexArray(L);

This will be referred to as the third graphics command sequence.

A description will be given, with reference to FIG. 3D, of a graphicscommand sequence generated by conversion from intermediate commandsusing the identity determination unit 60.

The identification unit 60 compares the first graphics command sequenceand the second graphics command sequence and determines whether the samegraphics command with the same state value is repeatedly generated.SetTexture(B) in the second graphics command sequence is the same typeof graphics command as SetTexture(A) in the first graphics commandsequence, but the commands differ in in the state value (B≠A).SetVertexShader(P) in the second graphics command sequence is the sametype of graphics command as SetVertexShader(P) in the first graphicscommand sequence, and the commands are identical in the state value(both commands include P). SetFragmentShader(Y) in the second graphicscommand sequence is the same type of graphics command asSetFragmentShader(X) in the first graphics command sequence, but thecommands differ in the state value (Y≠X). DrawIndexArray(K) in thesecond graphics command sequence is the same type of graphics command asDrawIndexArray(J) in the first graphics command, but the commands differin the state value (K≠J).

SetVertexShader(P) in the second graphics command sequence is the sametype of command as and is of the same state as SetVertexShader(P) in thefirst graphics command sequence, and so is a redundant command that neednot be executed. Thus, the graphics command generation unit 70 does notgenerate SetVertexShader(P) in the second graphics command sequencebased on the result of determination by the identity determination unit60, and generates the remaining commands SetTexture(B),SetFragmentShader(Y), and DrawIndexArray(K). In other words, if theidentity determination unit 60 is operated, the second graphics commandsequence generated by the graphics command generation unit 70 will be asfollows.

SetTexture(B);

SetFragmentShader(Y);

DrawIndexArray(K);

Similarly, the identification unit 60 compares the second graphicscommand sequence and the third graphics command sequence and determineswhether the same graphics command with the same state value isrepeatedly generated. SetTexture(B) in the third graphics commandsequence is the same type of graphics command as SetTexture(B) in thesecond graphics command sequence, and the commands are identical in thestate value (both commands include B). SetVertexShader(P) in the thirdgraphics command sequence is the same type of graphics command asSetVertexShader(P) in the second graphics command sequence, and thecommands are identical in the state value (both commands include P).SetFragmentShader(Y) in the third graphics command sequence is the sametype of graphics command as SetFragmentShader(Y) in the second graphicscommand sequence, and the commands are identical in the state value(both commands include Y). DrawIndexArray(L) in the third graphicscommand sequence is type same type of graphics command asDrawIndexArray(K) in the second graphics command, but the commandsdiffer in the state value (L≠K).

SetTexture(B), SetVertexShader(P), and SetFragmentShader(Y) in the thirdgraphics command sequence are the same type of command as and are of thesame state as SetTexture(B), SetVertexShader(P), andSetFragmentShader(Y) in the second graphics command sequence, and so areredundant commands that need not be executed. Thus, the graphics commandgeneration unit 70 does not generate SetTexture(B), SetVertexShader(P),and SetFragmentShader(Y) in the third graphics command sequence based onthe result of determination by the identity determination unit 60, andgenerates the remaining command DrawIndexArray(L). In other words, ifthe identity determination unit 60 is operated, the third graphicscommand sequence generated by the graphics command generation unit 70will be as follows.

DrawIndexArray(L);

To summarize the above, according to the graphics command conversionunit 50 of the embodiment, the identity determination unit 60 determinesthe identity of the states of the graphics commands. The graphicscommand generation unit 70 generates the following graphics commandsequence, in which redundancy is eliminated, from the intermediatecommand sequence sorted by the sorting unit 40, based on the result ofdetermination on identify.

SetTexture(A);

SetVertexShader(P);

SetFragmentShader(X);

DrawIndexArray(J);

SetTexture(B);

SetFragmentShader(Y);

DrawIndexArray(K);

DrawIndexArray(L);

In comparison with the case where the identity determination unit 60 isnot in operation as shown in FIG. 3C, the number of generated graphicscommands is reduced from 12 to 8 so that the processing efficiency isimproved.

A description will be given of the significance of sorting, as shown inFIG. 3B, the intermediate command sequence generated by the intermediatecommand generation unit 30 shown in FIG. 3A, by using the sorting unit40.

If it is assumed that the sorting unit 40 does not sort the intermediatecommand sequence, the graphics command sequence is generated accordingto the intermediate command sequence of FIG. 3A. Without the operationof the identity determination unit 60, the intermediate command sequencewill in this case be converted into the following graphics commandsequence.

SetTexture(B);

SetVertexShader(P);

SetFragmentShader(Y);

DrawIndexArray(K);

SetTexture(A);

SetVertexShader(P);

SetFragmentShader(X);

DrawIndexArray(J);

SetTexture(B);

SetVertexShader(P);

SetFragmentShader(Y);

DrawIndexArray(L);

If the identity determination unit 60 is in operation, the sixth commandSetVertexShader(P) in the above graphics command sequence is of the samestate as the second command SetVertexShader(P) executed previously andso can be deleted as a redundant command. Similarly, the tenth commandSetVertexShader(P) is of the same state as the sixth SetVertexShader(P)executed previously and so can be deleted as a redundant command.However, the other graphics commands differ in the state from thepreviously executed commands of the same type and so are not redundant.For example, the fifth command SetTexture(A) differs in the state fromthe first command SetTexture(B) executed previously, and the ninthcommand SetTexture(B) differs in the state from the fifth commandSetTexture(A) executed previously so that execution of these commandscannot be saved.

Therefore, only two graphics commands can be deleted as being redundantas a result of determination on identity by the identity determinationunit 60. The graphics command sequence generated by the graphics commandgeneration unit 70 with reduced redundancy will include 10 graphicscommands as indicated below.

SetTexture(B);

SetVertexShader(P);

SetFragmentShader(Y);

DrawIndexArray(K);

SetTexture(A);

SetFragmentShader(X);

DrawIndexArray(J);

SetTexture(B);

SetFragmentShader(Y);

DrawIndexArray(L);

Thus, by sorting the order of executing the intermediate commandsequence by the sorting unit 40, the number of graphics commandsdetermined by the identity determination unit 60 as being redundant canbe increased, and an optimized sequence of graphics commands withreduced redundancy can be generated by the graphics command generationunit 70 so that the efficiency of graphics processing can be improved.

A detailed description will be given of the process of sorting anintermediate command sequence according to transition cost.

FIG. 4A illustrates the method of computing a transition cost of modeldata by using the transition cost computation unit 10, and FIG. 4Billustrates the method of assigning a sort key to the model data byusing the sort key assigning unit 20.

The transition cost computation unit 10 computes the transition costindicating the processing cost imposed on the hardware for graphicscomputation performed when a given item of model data makes a transitionto another item of model data. For example, if the texture is changed asa result of transition of model data, the transition cost of 10 pointsis scored. If the fragment shader is changed, the transition cost of 30points is scored. If the vertex shader is changed, the transition costof 20 points is scored. These points indicate the relative load imposedon the graphics hardware when the texture, the fragment shader, or thevertex shader are changed.

For example, if three textures are changed and one fragment shader ischanged when a transition from model data A to model data B occurs, thetransition cost will be 10×3+30=60 points in total.

The transition cost computation unit 10 examines the model for allobjects rendered in each frame and computes the transition cost in atransition occurring between two items of model data. FIG. 4A shows anexample where four items of model data A-D are given, and the transitioncost between two arbitrary items of model data is computed. Thetransition cost from model data A to model data B is 10, the transitioncost from model data A to model data C is 30, the transition cost frommodel data A to model data D is 50, the transition cost from model dataB to model data C is 40, the transition cost from model data B to modeldata D is 20, and the transition cost from model data C to model data Dis 10.

The sort key assigning unit 20 starts with the model data that mostoccupies the displayed screen area (e.g., the model data that willoccupy the center of the screen), and scans all model data by repeatedlyselecting the model data with the least transition cost. The sort keyassigning unit 20 determines the sequence in which the model data shouldmake a transition and assigns the sort key to the model data inaccordance with the sequence of transition.

The reason that the sort key assigning unit 20 starts with the modeldata that will occupy the center of the screen is that, by renderingsuch model data first, the likelihood is increased that pixels generatedby subsequent intermediate commands are hidden behind so that associatedsteps can be skipped by culling and the processing efficiency isimproved accordingly.

In this case, it will be assumed that model data A occupies the centerof the screen so that sorting is started with model data A. As shown inFIG. 4B, the cost of transition from the starting model data A to modeldata B is 10 points, the cost of transition to model data C is 30points, and the cost of transition to model data D is 50 points.Therefore, model data B with the least transition cost among the threeitems of model data B, C, and D is selected as the second destination oftransition.

Similarly, the cost of transition from model data B to model data C is40 points, and the cost of transition to model data D is 20 points.Therefore, model data D with the least transition cost among the twoitems of model data C and D is selected as the third destination oftransition. Finally, a transition occurs from model data D to model dataC that remains. The cost of transition to the fourth model data C is 10.

Thus, the sort key assigning unit 20 determines the sequence A, B, D,and C in which the model data should make a transition, in accordancewith the transition cost between items of model data, and assigns sortkeys 0, 1, 2, and 3 to the items of model data A, B, D, and C,respectively.

In this example, the transition cost between two arbitrary items ofmodel data is computed. A given item of model data is defined as astarting data, and the minimum transition cost is identified so as todetermine the sequence of transition of model data and assign sort keysaccordingly. Alternatively, the sequence of transition of model data maybe determined according to the transition cost, by using an alternativesearch algorithm. Still alternatively, if a heavy processing load isimposed by exhaustively computing the transition cost between twoarbitrary items of model data, the transition cost may be determined forsome combinations of items of model data and the path for scanning modeldata may be limited to the range in which the transition cost isdetermined.

When the intermediate command generation unit 30 generates anintermediate command having model data and work data, a sort key isassigned to the model data. The sorting unit 40 sorts the intermediatecommand sequence generated by the intermediate command generation unit30 according to the order defined by the sort keys. This allowsintermediate commands with similar model data to be clustered andexecuted in succession.

By causing the model data to make a transition in the ascending order oftransition cost of the model data, the states of repeatedly executedgraphics commands in the graphics command sequence generated from theintermediate command sequence will more likely to match. For example,that the transition cost is smaller means that the texture or shader isless frequently changed and that the state of the graphics command isless frequently changed. For this reason, by sorting the intermediatecommand sequence in the ascending order of transition cost of the modeldata and then converting the intermediate command sequence into thegraphics command sequence, the number of graphics commands that can bedeleted as a result of identity determination can be increased.

FIG. 5 is a flowchart showing the steps of generating graphics commandsby the graphics command generation device 200 according to theembodiment.

Model data for all objects to be rendered is generated (S10). Thetransition cost computation unit 10 computes the transition costincurred when a transition occurs between model data (S20). The sort keyassigning unit 20 determines the sequence in which the model data shouldmake a transition in accordance with the transition cost and assignssort keys to the model data in the determined sequence (S30). StepsS10-S30 are executed off line, and the model data with the sort keysassigned is stored in the model data storage unit 32.

Steps S40-S70 are repeated for the frames. First, the intermediatecommand generation unit 30 generates an intermediate command havingmodel data and work data (S40). The sorting unit 40 sorts theintermediate commands generated by the intermediate command generationunit 30 in the sequence defined by the sort keys assigned to the modeldata (S50). The graphics command conversion unit 50 converts the sortedintermediate commands into graphics commands (S60). To render asubsequent frame (Y in S70), control is returned to step S40 so thatsteps S40-S60 are repeated. If the process is terminated in the currentframe (N in S70), the graphics command generation process is terminated.

FIG. 6 is a flowchart showing the details of conversion into graphicscommands in step S60 executed by the graphics command conversion unit50.

The identity determination unit 60 in the graphics command conversionunit 50 refers to the state cache 80, using the state of the graphicscommand about to be generated from the intermediate command as a key,and examines whether the state value is cached (S80).

When a cache hit of the state value occurs in the state cache 80 (Y inS82), it means that the graphics command with the same state value hasalready been executed. Therefore, the identity determination unit 60determines that the graphics command about to be generated from theintermediate command is redundant. The graphics command generation unit70 terminates the process without generating this graphics command.

Conversely, if a cache hit of the state value does not occur in thestate cache 80 (N in S82), it means that the graphics command about tobe generated from the intermediate command was executed previously witha different state value or the graphics command has not been executedyet. In this case, the identity determination unit 60 determines thatthe graphics command about to be generated from the intermediate commandis not redundant and updates the state cache 80 with the state value(S84). The graphics command generation unit 70 generates the graphicscommand from the intermediate command (S86).

The identity determination unit 60 and the graphics command generationunit 70 repeat the steps S80-S86 by using the state cache 80, andconverts the intermediate command sequence into the graphics commandsequence accordingly. This generates the graphics command sequence inwhich redundant graphics commands defining the same setting are removed.

Specific examples of the types of state cached in the state cache 80will be given below.

(1) Program ID of the fragment shader/vertex shader

A unique ID is assigned to fragment shader programs and vertex shaderprograms as they are generated and is stored in the state cache 80. Theidentity determination unit 60 determines that program setting commandsare redundant if their IDs are identical, and the graphics commandgeneration unit 70 skips generation of one of the program settingcommands. In case that the shader is located in a single logical addressspace, the ID may be the start address of the space.

(2) Texture ID A unique ID is assigned to a texture as it is generated.The state cache 80 stores the ID for each texture unit. The identitydetermination unit 60 checks the IDs of texture units at the time ofrendering. If the IDs are identical, the identity determination unit 60determines that the texture setting commands are redundant, and thegraphics command generation unit 70 skips generation of one of thetexture setting commands. In case that the texture is located in asingle logical address space, the ID may be the start address of thespace.

(3) Setting values of depth test/blend/stencil test

The setting as to whether to perform a depth test, blend, and a stenciltest is stored in the state cache 80 in the form of a Bool value. If thesetting values are identified as being equal, the identity determinationunit 60 determines that the associated commands for setting whether toperform a depth test, blend, and a stencil test are redundant. Thegraphics command generation unit 70 skips generation of one of thesetting commands. (4) Depth test function/blend function/stencil testoperator A constant meaning a defined function is cached in the statecache 80. In the case of a depth test function, a constant identifyingwhether the depth function is set to equal (=), less than (<), orgreater than (>) is stored in the state cache 80. In the case of a blendfunction, a constant identifying a blend ratio is stored. In the case ofa stencil test operator, a constant identifying increment or decrementis stored. The identity determination unit 60 determines that functionsetting commands are redundant if the constants identifying thefunctions are identical, and the graphics command generation unit 70skips generation of one of the setting commands.

(5) Matrices IDs are assigned to respective matrices, and the statecache 80 stores the IDs. The identity determination unit 60 determinesthat setting commands for matrices are redundant if their IDs areidentical, and the graphical command generation unit 70 skips generationof one of the matrix setting commands. For example, in the case of aView matrix or a Projection matrix, substantially the only switchingduring rendering occurs between shadow map rendering and normalrendering. In many cases, therefore, generation of a matrix settingcommand can be skipped.

In summary, the states cached in the cache state 80 are as follows.

View Matrix ID

Projection Matrix ID

Model Matrix ID

Fragment Shader ID

Vertex Shader ID

Texture ID

Depth Test (Enable/Disable)

Depth Test Function

Stencil Test(Enable/Disable)

Stencil Test Function

Blend (Enable/Disable)

Blend Function

As described above, according to the graphics command generation device200 of the embodiment, intermediate commands sorted according to thetransition cost of model data are successively converted into graphicscommands. In the process of conversion into graphics commands, thenumber of graphics commands generated is reduced and the processingefficiency is improved by caching the state values defined by thegraphics commands and generating graphics commands only when the definedstate value changes. The GPU hardware is designed to perform a deeppipeline operation. If any of the states changes, stall occurs towardsan early stage in the pipeline so that the system should await an updateto the state. According to the embodiment, reduction in performanceassociated with context switching inside the GPU hardware can bemitigated so that a larger amount of data can be rendered thanotherwise.

A description will be given, with reference to FIGS. 7-9, of severalapplications of the graphics command generation device 200 according tothe embodiment.

FIG. 7 shows a system where an intermediate command sequence isgenerated in a plurality of processes, and sorting and elimination ofredundancy are performed in a single rendering process.

A plurality of processes A-C generate intermediate command sequences forrendering in parallel. A unique ID management process that assigns IDsto resources such as a texture, a shader or others is located in thesystem and manages the system so that unique resource IDs are usedthroughout the system. Each of the processes A-C inquires the unique IDmanagement process about the ID of the resources and assigns sort keysto the model data. The intermediate command sequence generated by eachof the processes A-C is delivered to the single rendering process. Therendering process ultimately sorts the intermediate command sequenceaccording to the sort keys, converts the intermediate command sequenceinto the graphics command sequence, and eliminates redundancy throughidentity determination based on the state.

In this case, the functions of the transition cost computation unit 10,the sort key assigning unit 20, and the intermediate command generationunit 30 of the graphics command generation device 200 are implemented inthe processes A-C, but the functions of the sorting unit 40, theidentity determination unit 60, and the graphics command generation unit70 are implemented in the single rendering process.

An advantage of this application is that the process can be distributedby using a plurality of processes so that the processing efficiency isimproved.

FIG. 8 shows a system where intermediate command sequences for renderingare generated by a plurality of servers, and sorting and redundancyelimination are performed in a client which communicates with theserver.

The service provider assigns IDs to the resources such as a texture, ashader or others and manages the resources. The servers A-C generateintermediate command sequences for rendering in parallel and deliversort keys for the model data to the application in a client along withthe content, allowing the client to sort the intermediate commands andgenerate graphics command in which redundancy is eliminated.

In this case, the functions of the transition cost computation unit 10,the sort key assigning unit 20, and the intermediate command generationunit 30 of the graphics command generation device 200 are implemented inthe servers A-C, but the functions of the sorting unit 40, the identitydetermination unit 60, and the graphics command generation unit 70 areimplemented in the client.

An advantage of this application is that the load imposed by renderingon the client can be reduced, the rendering efficiency of the client canbe improved, and the power consumption in the client is reduced.

FIG. 9 shows a system where intermediate command sequences are generatedby a plurality of clients, and sorting and redundancy elimination areperformed in a server which communicates with the plurality of clients.

The client creates a model comprising a combination of model datacreated by the service provider in advance, and sends the renderingintermediate command to the server. The server acknowledges theintermediate commands created by the plurality of clients A-C andrenders the commands on one screen. For example, when a large image isrendered, a plurality of clients are often used to generate intermediatecommands in parallel so that the server receives the intermediatecommands from the plurality of clients A-C and renders the imageaccordingly.

The server sorts the intermediate commands received from the pluralityof clients A-C. The server converts the intermediate commands into agraphics command sequence such that redundant graphics commands areeliminated. The server then uses the graphics commands for rendering.

Ultimately, the server delivers the rendered image to the clients A-C.The image includes model data transmitted by other clients.

In this case, the functions of the transition cost computation unit 10,the sort key assigning unit 20, and the intermediate command generationunit 30 of the graphics command generation device 200 are implemented inthe clients A-C, but the functions of the sorting unit 40, the identitydetermination unit 60, and the graphics command generation unit 70 areimplemented in the server.

In this application, power consumption and computing resources of theserver can be reduced.

Described above is an explanation based on an exemplary embodiment. Theembodiment is intended to be illustrative only and it will be obvious tothose skilled in the art that various modifications to constitutingelements and processes could be developed and that such modificationsare also within the scope of the present invention.

What is claimed is:
 1. A graphics command generating device comprising:an intermediate command generation unit configured to generateintermediate commands, which are intermediate rendering commands havingmodel data for rendering an object; and a graphics command conversionunit configured to convert the generated intermediate commands into agraphic command sequence for execution by a graphics processor, whereinthe graphics command conversion unit comprises: an identitydetermination unit configured to determine whether a state of a graphicscommand to be generated from an intermediate command is the same as astate of a graphics command generated previously; and a graphics commandgeneration unit configured to generate a graphics command determined bythe identity determination unit as not having a state that is the same,and to not generate a graphics command determined as having the samestate, defining said command as a redundant command.
 2. The graphicscommand generation device according to claim 1, wherein the graphicscommand conversion unit further comprises a state cache configured tocache a state of a graphics command generated by the graphics commandgeneration unit, wherein the identity determination unit refers to thestate cache, using a state of a graphics command to be generated from anintermediate command as a key, determines, in the event of a cache hit,that the state of the graphics command to be generated from theintermediate command is the same as a state of a graphics commandgenerated previously, and updates, in the absence of a cache hit, thecache with the state of the graphics command to be generated from theintermediate command.
 3. The graphics command generation deviceaccording to claim 1, further comprising: a transition cost computationunit configured to compute a transition cost indicating a load imposedon hardware involved in graphics computation as a result of changingmodel data for rendering an object; a sort key assigning unit configuredto determine a sequence in which the model data should make a transitionbased on the transition cost, and to assign sort keys to respectiveitems of model data in accordance with the determined sequence oftransition; and a sorting unit configured to organize a sequence ofexecution of a plurality of intermediate commands generated by theintermediate command generation unit in accordance with the sort keyassigned to the model data of the intermediate commands, wherein thegraphics command generation unit converts the plurality of intermediatecommands, the sequence of which is organized by the sorting unit, into agraphics command sequence.
 4. The graphics command generation deviceaccording to claim 3, wherein the sort key determination unit startswith a given item of model data and determines the sequence in which themodel data should make a transition by scanning the model data in theascending order of the transition cost.
 5. The graphics commandgeneration device according to claim 3, wherein the sorting unit startswith the model data that most occupies the displayed screen area anddetermines the sequence in which the model data should make a transitionby scanning the model data in the ascending order of the transitioncost.
 6. A graphics command generation method comprising: generatingintermediate commands, which are intermediate rendering commands havingmodel data for rendering an object; and converting the generatedintermediate commands into a graphic command sequence for execution by agraphics processor, wherein said converting comprises: determiningwhether a state of a graphics command to be generated from anintermediate command is the same as a state of a graphics commandgenerated previously; and generating a graphics command determined asnot having a state that is the same, and not generating a graphicscommand determined as having the same state, defining said command as aredundant command.
 7. A non-transitory computer-readable recordingmedium encoded with a graphics command generation program comprising: ageneration module configured to generate intermediate commands, whichare intermediate rendering commands having model data for rendering anobject; and a graphics command conversion module configured to convertthe generated intermediate commands into a graphic command sequence forexecution by a graphics processor, wherein said graphics commandconversion module comprises: an identity determination module configuredto determine whether a state of a graphics command to be generated froman intermediate command is the same as a state of a graphics commandgenerated previously; and a graphics command generation moduleconfigured to generate a graphics command determined by the identitydetermination module as not having a state that is the same, and to notgenerate a graphics command determined as having the same state,defining said command as a redundant command.